ANCA negative vasculitis among the following is
**Core Concept**
ANCA (Anti-Neutrophil Cytoplasmic Antibodies) negative vasculitis refers to a group of systemic vasculitides that do not involve the presence of ANCA. These conditions are typically characterized by inflammation of the blood vessels and can affect various organs. The clinical presentation and treatment of ANCA-negative vasculitis differ from those of ANCA-associated vasculitis.
**Why the Correct Answer is Right**
The correct answer is **Microscopic Polyangiitis (MPA)**. MPA is a type of ANCA-negative vasculitis that primarily affects small-sized blood vessels. It is characterized by the presence of pauci-immune necrotizing glomerulonephritis and pulmonary capillaritis. The pathophysiology of MPA involves the activation of immune cells, release of cytokines, and deposition of immune complexes in the vessel walls, leading to inflammation and damage.
**Why Each Wrong Option is Incorrect**
* **Option A:** **Granulomatosis with Polyangiitis (GPA)** is an ANCA-associated vasculitis, characterized by the presence of c-ANCA (PR3-ANCA) and involves the upper and lower respiratory tracts, kidneys, and other organs.
* **Option B:** **Eosinophilic Granulomatosis with Polyangiitis (EGPA)** is also an ANCA-associated vasculitis, characterized by the presence of p-ANCA (MPO-ANCA) and involves asthma, eosinophilia, and vasculitis affecting various organs.
* **Option C:** **Polyarteritis Nodosa (PAN)** is a medium-sized vessel vasculitis that is ANCA-negative and typically affects the kidneys, liver, and other organs.
**Clinical Pearl / High-Yield Fact**
MPA is often associated with renal involvement, and patients may present with rapidly progressive glomerulonephritis (RPGN) and hematuria. The diagnosis of MPA is based on clinical findings, laboratory tests (e.g., ANCA negativity), and biopsy results.
**Correct Answer:** C. Polyarteritis Nodosa (PAN)